The present invention relates to improvements in key buttons for use in an electronic device.
A push button switch used in a desk-top type electronic calculator and the like has a plurality of key buttons which makes contact or breaks contact through depression of the button. In these switches, the contacts are normally biased in the open condition by a release resilient body. Upon depression of the buttons, the contacts are closed.
A structure of a conventional push button type switch is illustrated in FIG. 1. As shown, a key button 2 is placed in an opening portion of an electronic calculator, being movable up and down. A resilient member 4 with an upwardly swelled portion having a downward expansion 3 which comes in contact with the bottom surface of the key button 2, is provided under the key button 2. A conductive rubber sheet 6 and an insulating sheet 7 for a movable contact are layered between the resilient member 4 and a substrate 5. The insulating sheet 7 is partly cut away right under the expansion 3 and a fixed contact 8 is fitted in this cut-away portion.
When the key button 2 is depressed, the expansion 3 presses down the conductive sheet 6 to be in contact with the fixed contact 8.
The key button 2 is provided with a collar 9 outwardly extending at the bottom end of the button 2, in order to prevent the key button from coming out of the case 1. Conventionally, the collar 9 is molded by using synthetic resin and is integral with the button 2. Alternately, a metal plate is subjected to a drawing or a rolling press working and is molded. However, the button thus formed is fragile at the collar 9 and thus is disadvantageous in its mechanical strength. For this reason, the collar 9 of the key board, which is an important factor to determine the thickness of the key board of the electronic calculator, cannot be made very thin. Therefore, it is difficult to manufacture a thin key button used for a small-sized electronic calculator which is prevailing currently in this field. Alternately, the button portion to be depressed and the collar portion are separately manufactured and these separate portions are bonded or welded. The former, however, is expensive and the latter has a poor appearance.